The present invention relates generally to fuel atomizers and more particularly to a supersonic coal water slurry fuel atomizer.
Twin fuel atomizers are designed to break up a stream of liquid by contacting it with gas or steam traveling at a high velocity. The degree of break up of the liquid is achieved through the type of nozzle utilized for atomization. It is important that the characteristics of the nozzle remain constant in order to provide a constant degree of atomization. However, the liquid which is being atomized may be abrasive which ultimately leads to erosion of the nozzle and deterioration of the nozzle's properties.
Nozzles for atomizing fuel are utilized in various fields for various purposes. The twin fluid atomizer may comprise a liquid supply tube surrounded by a coaxial gas supply tube. Traditional twin fluid atomizers are subject to erosion. Erosion is especially apparent in twin fluid atomizers which atomize coal water slurry.
Coal water slurries generally comprise a liquid carrier and a solid carbonaceous fuel. The coal water slurry is highly abrasive due to the presence of the solid carbonaceous fuel. In the traditional twin fluid atomizers, high velocities of the coal water slurry are necessary for atomization which leads to severe erosion of exposed portions of the atomizer. Such erosion ultimately destroys the properties of the atomizer.
Erosion is not the only problem encountered with traditional twin fluid atomizers. Another problem with traditional twin fluid atomizers is that the secondary fluid used to atomize the coal water slurry is typically compressed air or steam at pressures between 50 to 100 psi or greater. A high pressure pump is required to inject the coal water slurry at a pressure above the pressure of the secondary fluid. High pressure pumps are expensive and can subject the coal water slurry to a high degree of shear and thereby degrade shear sensitive slurries before they enter the atomizer. Degradation of the slurries is not desirable.
U.S. Pat. No. 4,171,091 discloses a twin fuel sprayer comprising a liquid supply tube surrounded by a coaxial gas or gas mixture supply tube. Since the device mixes fuel inside the sprayer, the sprayer is subjected to erosion. PG,4
U.S. Pat. No. 4,762,532 also discloses a twin-fluid nozzle which may combine a carbonaceous slurry and a gas. The nozzle is made adjustable so as to provide a substantially constant mixing energy.
Other devices are known for achieving atomization. Although these devices have their advantages, they suffer from a number of problems such as erosion within the nozzle, plugging of the nozzle, the need for high pressure pumps, etc.
There continues to be a need for coal water slurry atomizers which overcome the shortcomings of the prior art.